The aims of this project are: 1. To characterize the composition of gallstones, gallbladder and hepatic bile in patients with Sickle Cell Disease and to compare the concentrations of these components to those found in patients with Sickle Trait and controls. 2. To determine the role of biliary tract infection in the development of gallstones. 3. To relate the biliary bilirubin and lipid composition to serum unconjugated bilirubin and the rate of bilirubin production. 4. To compare the pattern of bile flow and composition and bilirubin and bile salt kinetics in patients with and without Sickle Cell Disease who have balloon-occludible reinfusion T-tubes or in volunteers utilizing balloon-occludible intestinal tubes. 5. To assess the effect of sickle cell crisis on bilirubin and bile salt kinetics by comparing the composite of bile-rich duodenal fluid in patients with Sickle Cell Disease during and between crises.